The present invention relates generally to buckles, and more particularly to end-fitting buckles that may be used to secure webbing.
End-fitting buckles are used to secure one end of webbing to an object. For example, webbing may be attached to some wheelchairs to strap a patient into a seated position in the wheelchair. If used in this manner, the webbing typically requires a length adjustment by a professional in order to properly fit the patient. In many applications, it is desirable that the webbing setting not be carelessly changed after set by the professional.
Although some prior art end-fitting buckles work well for their intended purpose, there are a few problems inherent in their use, especially when precise webbing length adjustments must be established and maintained. For most end-fitting buckles, after the webbing has been threaded through the end-fitting buckle, pulling on the load end of the webbing usually does not affect the professionally-set setting. However, the webbing length may be accidentally changed from the setting by simply pulling the loose, or free, end of the webbing. If a user accidentally or carelessly pulls on the free end and changes the setting, a professional is once again needed to properly reset the webbing length.
For many prior art end-fitting buckles, constant tension on the load end is required to maintain the webbing setting. However, for many applications, tension in the webbing may be intermittently released during use, causing the webbing setting to be lost, and requiring resetting of the webbing length.
In addition to the above problems, most prior art end-fitting buckles are designed to function properly only when used with webbing of a specific thickness. For these buckles, webbing which is too thin or thick tends to slip under tension or cannot be threaded through the buckle at all. Moreover, even if a proper thickness is used, many prior art end-fitting buckles are designed so that threading webbing through the end-fitting buckle is awkward and confusing.
The present invention provides an end-fitting buckle that permits versatile and secure connection to an end of a webbing. The end-fitting buckle includes a cam cover that rotates to allow webbing to be inserted when the cam cover is in a fully opened position. Once inserted, the free end of the webbing is pulled to tighten the webbing on the load end while the cover is in an intermediate position. The cover may then be closed to lock both the free end and the load end.
The end-fitting buckle includes a sliding, knurled bar, around which the webbing is threaded. The free end of the webbing extends over the sliding, knurled bar, then down and under a cam surface on the cam cover. In both the intermediate and locked positions, the cam surface forces the free end of the webbing into contact with the load end of the webbing. In the intermediate position, only a partial, flat edge of the cam cover is in contact with the free end (i.e., top layer) of the webbing. Pulling on the load end causes the sliding, knurled bar to slide toward the cam surface of the cam cover, pinching the free end between the cam surface and the sliding, knurled bar. Further pulling force on the load end tightens the clamping of the free end between the sliding, knurled bar and the cam surface, preventing retraction of the webbing in the load end direction.
While the buckle is in the intermediate position, the webbing may be pulled at the free end to cinch the webbing in place. Pulling the webbing in this direction releases the pinching effect of the sliding, knurled bar and the cam surface on the free end, because the cam surface extends below the sliding, knurled bar, and pulling out on the free end puts a downward, rearward force on the sliding, knurled bar, moving it slightly away from the cam surface and releasing the free end.
When the cover is closed, movement of the free end of the webbing is prevented by teeth in the cam cover. The teeth lock the free end into place, holding the set position of the webbing.
The sliding, knurled bar allows easy feeding of the webbing, and permits different thicknesses of webbing to be used with the buckle. The cover design also provides use of varied thicknesses of webbing, because the cam action of the cover utilizes friction between the sliding, knurled bar and the cam surface, instead of a pinching action of the two webbing ends together.
The teeth press the webbing and sliding, knurled bar forward to tightly engage with the cam section of the cover, thus preventing loosening when tension is released from the load end of the webbing. This positive engagement is ensured by a snap-locking feature at the rear of the cover, which may close with an audible click to indicate proper locking. Unlocking the cover may require the use of a flat tool such as a screwdriver or a coin, thereby preventing accidental release of the webbing.
Other features are provided in the buckle of the present invention. A hump in the base plate for the end-fitting buckle may be provided for forcing the webbing upward and thereby promotes easier feeding. The cover acts as a spring to ensure proper engagement of the teeth with the webbing across a wide range of thicknesses, and slightly deforms against the spring action to close and snap the cover into place. The cover is configured such that force applied to the webbing causes the cover to tighten on the frame of the end-fitting buckle.